Acoustic origins of individual differences in sound localization behavior

Abstract

Human listeners vary widely in their ability to localize unfamiliar sounds in an environment devoid of visual cues. Our research, in which blindfolded listeners give numerical estimates of apparent source azimuth and elevation, suggests that individual differences are greatest in judgments of source elevation; listeners are uniformly accurate when judging source azimuth. The pattern of individual differences is the same for free-field sources and for simulated free-field sources presented over head-phones. Simulated free-field sources are produced by digital filtering techniques which incorporate the listener-specific, direction-dependent acoustic effects of the outer ears. Two features of this data bear on the question of the origin of individual differences in elevation accuracy: (1) a listener's accuracy in judging source elevation can be predicted from an analysis of the acoustic characteristics of the listener's outer ears; (2) the pattern of elevation errors made by one listener (A) can be transferred to another listener (B) by presenting to listener B the simulated free-field sources derived from the outer-ear acoustics of listener A. Thus it is believed that many of the individual differences in localization behavior are traceable to individual differences in outer-ear acoustics. The data have important implications for the study of localization in both basic and applied contexts. [Work supported by NASA, NSF, and USAF-AAMRL-AFSC.]